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Date: Sat, 30 Jan 1999 00:49:58 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199901291349.AAA06463@godzilla.zeta.org.au>
To: brian@Awfulhak.org, dillon@FreeBSD.ORG
Subject: Re: cvs commit: src/sys/sys kernel.h
Cc: cvs-all@FreeBSD.ORG, cvs-committers@FreeBSD.ORG
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>A similar thing is the more fundamental problem with const - there's no 
>way of declaring a function that accepts ``const something *'' and 
>returns ``whatever was passed *''.

You mean ``whatever the type was before it was passed''.

>Does anyone know if gcc has an ``extension'' to deal with this ?  For 

It has the non-useful extension g++ :-).

>example, the strchr() prototype is wrong because I can
>
>  const char *donttouch;
>  char dowhatyouwant;
        ^*
>
>  ....
>  dowhatyouwant = strchr(donttouch, *donttouch);

You can do that anyway by casting away the const.  Don't do that.

>The prototype is doubly wrong because there's no correct way to write
>the function - not without casting the const char * to a char *.

There is no problem with implementing strchr(), only a minor problem
with its use.  Casting the const char * to char * is a correct way of
implementing it.

A similar problem with the strtoul() family was "fixed" by breaking
the kernel versions to take a `const char **endptr' instead of a
`char *endptr' and propagating the breakage to all callers.  This
should be backed out.  The warning can be avoided using a union hack.

Bruce

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